Vehicle display device

ABSTRACT

A vehicle display device includes a conversion block that converts, based on correction data stored in a memory, an imaging pixel value in a camera image acquired by an outside camera into a correction pixel value in accordance with outside brightness detected by a brightness sensor, and a display control block that controls a light source luminance value of the head-up display in correspondence with the correction pixel value converted from the imaging pixel value by the conversion block.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalPatent Application No. PCT/JP2018/001852 filed on Jan. 23, 2018, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2017-31371 filed on Feb. 22, 2017.

TECHNICAL FIELD

The present disclosure relates to a vehicle display device for visuallydisplaying a display image as a virtual image in a visual recognitionregion in a vehicle compartment by projecting the display image onto aprojection member that transmits an outside scenery.

BACKGROUND

Conventionally, a vehicle display device may project a display imageonto a projection member using light emitted from a head-up display(HUD: Head-Up Display). In these types of vehicle display devices, thereis a concern that luminance from the outside may adversely affect thevisibility of the projected image.

SUMMARY

According to a first aspect of the present disclosure, a vehicle displaydevice is provided in a vehicle mounted with an outside camera thatacquires a camera image by imaging outside scenery and a brightnesssensor that detects an outside brightness of the outside scenery, thevehicle display device is configured to project a display image onto aprojection member, which transmits the outside scenery, to display thedisplay image as a visible virtual image in a visual recognition regionin a vehicle compartment, the vehicle display device including a head-updisplay that emits light to form the display image, a memory thatstores, as correction data, a correlation of a correction pixel valuewith respect to an imaging pixel value, the correction pixel value beingconverted from the imaging pixel value forming the camera image by acorrection according to the outside brightness, a conversion block thatconverts, based on the correction data stored in the memory, the imagingpixel value in the camera image acquired by the outside camera into thecorrection pixel value in accordance with the outside brightnessdetected by the brightness sensor, and a display control block thatcontrols a light source luminance value of the head-up display incorrespondence with the correction pixel value converted from theimaging pixel value by the conversion block.

According to a vehicle display device of a second aspect of the presentdisclosure, a display image is virtually displayed by a head-up displaywithin a display region. Further, this display region is included in animaging region of an outside camera and a detection region of abrightness sensor.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is an internal view showing a vehicle compartment of a hostvehicle equipped with a vehicle display device according to a firstembodiment;

FIG. 2 is a block diagram showing the vehicle display device accordingto the first embodiment,

FIG. 3 is an image diagram showing a camera image according to the firstembodiment,

FIG. 4 is a block diagram showing a configuration of an HUD according tothe first embodiment,

FIG. 5 is a front view showing a virtual image display state of adisplay image according to the first embodiment,

FIG. 6 is an image diagram showing an imaging pixel value of the cameraimage according to the first embodiment;

FIG. 7 is a flowchart showing a display control flow according to thefirst embodiment,

FIG. 8 is an image diagram showing correction data according to thefirst embodiment,

FIG. 9 is a graph showing a correlation between a light source luminancevalue and an initial setting value according to the first embodiment,

FIG. 10 is an image diagram showing luminance value control dataaccording to the first embodiment,

FIG. 11 is a flowchart showing a display control flow according to thesecond embodiment,

FIG. 12 is an image diagram showing an imaging pixel value of a cameraimage according to the second embodiment,

FIG. 13 is a flowchart showing a display control flow according to athird embodiment,

FIG. 14 is an image diagram showing an imaging pixel value of a cameraimage according to the third embodiment;

FIG. 15 is a flowchart showing a display control flow according to afourth embodiment,

FIG. 16 is an image diagram showing an imaging pixel value of a cameraimage according to the fourth embodiment,

FIG. 17 is a flowchart showing a display control flow according to afifth embodiment,

FIG. 18(a) is a graph showing a correlation between a light sourceluminance value and an initial setting value according to a fifthembodiment,

FIG. 18(b) is a graph showing a correlation between a display pixelvalue and an initial setting value according to a fifth embodiment,

FIG. 19(a) is an image diagram showing luminance value control dataaccording to a fifth embodiment,

FIG. 19(b) is a graph showing pixel value control data according to afifth embodiment,

FIG. 20 is a block diagram showing a vehicle display device according toa modification of FIG. 2,

FIG. 21 is an image diagram showing an imaging pixel value of a cameraimage according to a modification of FIG. 6, and

FIG. 22 is an image diagram showing correction data according to amodification of FIG. 8.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a plurality of embodiments of the present disclosure willbe described with reference to the drawings, Incidentally, the samereference numerals are assigned to the corresponding components in eachembodiment, and thus, duplicate descriptions may be omitted. When only apart of the configuration is described in each embodiment, theconfiguration of the other embodiments described above can be applied toother parts of the configuration. Further, not only the combinations ofthe configurations explicitly shown in the description of the respectiveembodiments, but also the configurations of the plurality of embodimentscan be partially combined even if the configurations are not explicitlyshown if there is no problem in the combination in particular.

First Embodiment

First, consider a reference example vehicle display device that projectsa display image onto a projection member using light emitted from ahead-up display. In this reference example, a camera image is acquiredby capturing an outside scenery as a background of the display imagewith an outside camera so that a background luminance representing theoutside brightness of the external scene can be specified. Thebackground luminance specified from the camera image as described aboveis used in the control of the virtual image display luminance fordisplaying the display image virtually by the HUD, thereby making itpossible to reduce the deterioration of the visibility of the displayimage.

However, in order to properly acquire a camera image, in general, thereis a need to perform a filtering process such as an exposure control anda gain control in accordance with the outside brightness in an outsidecamera. For that reason, in spite of day and night having differentoutside brightness, imaging pixel values forming the camera image havethe same value or a close value depending on the filtering process, as aresult of which, in the reference example device described above, thespecified background luminance may not reflect an actual outsidebrightness. This leads to a concern that a contrast defect occurs inwhich the contrast of the display image with respect to the outsidescenery is insufficient or excessive, thereby making it difficult toreduce the visibility deterioration.

In this regard, a driving support system 1 according to a firstembodiment of the present disclosure is mounted on a vehicle 2 as shownin FIGS. 1 and 2. The driving support system 1 includes a peripherymonitoring system 3, a vehicle control system 4, and a vehicle displaydevice 5. Those elements 3, 4, and 5 are connected to each other throughan in-vehicle network 6, such as a LAN (Local Area Network), forexample.

As shown in FIG. 2, the periphery monitoring system 3 includes aperiphery sensor 30 and a periphery monitoring ECU (Electronic ControlUnit) 31. The periphery sensor 30 detects, for example, other obstaclessuch as other vehicles, artificial structures, humans and animals, whichmay collide in the outside of the vehicle 2, and traffic signs such asvelocity signs and various warning signs present in the outside of thevehicle 2 (i.e., outside the vehicle compartment 2 a). The peripherysensor 30 is, for example, one or a plurality of types including atleast the outside camera 30 a, among the outside camera 30 a, the sonar,the radar, the LIDAR (Light Detection and Ranging/Laser ImagingDetection and Ranging, and the like.

In this example, an outside camera 30 a, which is generally mounted onthe vehicle 2, acquires a camera image 33 by capturing an image of apredetermined range of an outside scenery 8 existing in front of avehicle compartment 2 a in an external environment of the vehicle 2shown in FIG. 3. The outside camera 30 a is, for example, a monoculartype or a compound eye type, and is mounted on a bumper 23, an innerrearview mirror 24, or the like of the vehicle 2 shown in FIGS. 1 and 4.As a result, an imaging region Ac of the outside camera 30 a shown inFIG. 5 is set in an area of the outside scenery 8 which can be visuallyrecognized by an occupant on a driver's seat 20 through a frontwindshield 21 of the vehicle 2 in the vehicle compartment 2 a.

As shown in FIG. 6, the camera image 33 acquired by the outside camera30 a is configured by imaging pixel values Tc of multiple colors.Therefore, the imaging pixel value Tc of the present embodimentrepresents a gradation value sensed by each pixel of the outside camera30 a for each of the colors of red (R), green (G) and blue (B) in 256gradations of 0 to 255. In other words, the outside camera 30 a of thepresent embodiment generates the imaging pixel value Tc of each pixel inan RGB data format.

The periphery monitoring ECU 31 shown in FIG. 2 mainly includes amicrocomputer having a processor and memories, and is connected to theperiphery sensor 30 and the in-vehicle network 6. The peripherymonitoring ECU 31 acquires, for example, obstacle information, trafficsign information, and the like based on an output signal from theperiphery sensor 30.

The vehicle control system 4 includes a vehicle-related sensor 40, anoccupant-related sensor 41, and a vehicle control ECU 42. Thevehicle-related sensor 40 is connected to the in-vehicle network 6. Thevehicle-related sensor 40 acquires, for example, driving stateinformation, navigation information, traffic sign information, drivingenvironment information, and the like of the vehicle 2. Thevehicle-related sensor 40 is, for example, one or multiple typesincluding at least a brightness sensor 40 a among the brightness sensor40 a, a vehicle speed sensor, a rotational speed sensor, a steeringangle sensor, a fuel sensor, a water temperature sensor, a communicationdevice, and the like.

In this example, the brightness sensor 40 a, which is generally mountedon the vehicle 2, detects the illuminance or luminance of apredetermined range of the outside scenery 8 existing in front of thevehicle compartment 2 a in the outside of the vehicle 2 shown in FIGS. 1and 5, as an outside brightness Lo. The brightness sensor 40 a is, forexample, a phototransistor, a photodiode, or the like, and is mounted onan instrument panel 22, the inner rearview mirror 24, or the like of thevehicle 2 shown in FIGS. 1 and 4, As a result, a detection region Al ofthe brightness sensor 40 a shown in FIG. 5 is set in an area of theoutside scenery 8, which can be visually recognized by the occupantthrough the front windshield 21 and included in the imaging region Ac ofthe outside camera 30 a.

As shown in FIG. 2, the occupant-related sensor 41 is connected to thein-vehicle network 6. The occupant-related sensor 41 detects a state oroperation of the occupant who has been present in the vehiclecompartment 2 a of the vehicle 2. The occupant-related sensor 41 is, forexample, one or multiple types including at least a power switch 41 aamong the power switch 41 a, a display setting switch, an occupant statemonitor, a turn switch, and the like.

In this example, the power switch 41 a is operated by an occupant insideor outside the vehicle compartment 2 a to start an internal combustionengine or a motor generator of the vehicle 2, thereby detecting theoperation. The power switch 41 a includes, for example, one type ormultiple types of a rotational operation type and a push operation typeby an occupant, a remote operation type by an electronic key, and thelike.

The vehicle control ECU 42 mainly includes a microcomputer having aprocessor and memories, and is connected to the in-vehicle networks 6.The vehicle control ECU 42 includes one or plural types of an enginecontrol ECU, a motor control ECU, a brake control ECU, a steeringcontrol ECU, an integrated control ECU, and the like.

As shown in FIGS. 1, 2, and 4, the vehicle display device 5 includes anHUD 50 and an HCU (HMI (Human Machine Interface) Control Unit)) 54 fordisplaying a display image 56 as a virtual image in the vehiclecompartment 2 a.

The HUD 50 is installed in the instrument panel 22 in the vehiclecompartment 2 a, The HUD 50 forms a color display image 56 by lightemitted from a projector 51. Therefore, as shown in FIGS. 2 and 4, theprojector 51 of the present embodiment is configured by combining adisplay unit 51 a and a light source unit 51 b together. In thisexample, the display unit 51 a mainly includes, for example, a dotmatrix type TFT liquid crystal panel or the like. The display unit 51 aforms the display image 56 by driving the respective pixels inaccordance with a display pixel value Td controlled by the HCU 54. Onthe other hand, the light source unit 51 b mainly includes an LED (LightEmitting Diode), for example. The light source unit 51 b is energizedaccording to a light source luminance value Sd controlled by the HCU 54to illuminate the display unit 51 a and emit a light of the displayimage 56. With the configuration described above, a virtual imagedisplay luminance Ld of the entire display image 56 shown in FIG. 5 isdetermined by the combination of the display pixel value Td of eachpixel of the display image 56 formed in the display unit 51 a and thelight source luminance value Sd of the light source unit 51 b that emitsthe light of the display image 56 together.

The displayed image 56 formed by the projector 51 in a light emissionstate represents various information to be notified the occupant of inthe vehicle compartment 2 a. Specifically, the display image 56represents, for example, not only driving state information such asvehicle speed information and engine speed information shown in FIGS. 1and 5, but also navigation information such as route guidanceinformation and traffic congestion information, traffic sign informationsuch as speed sign information, and driving environment information suchas weather information and road surface information. In addition tothose pieces of information, the display image 56 may represent, forexample, music information, video information, mobile communicationinformation, and the like provided in the vehicle compartment 2 a.

A light beam of the display image 56 formed by the projector 51 so as torepresent predetermined information is guided by an optical system 52such as a concave mirror as shown in FIGS. 1 and 4, thereby beingprojected onto the front windshield 21 as a projection member. At thattime, the front windshield 21 made of a light transmissive glasstransmits the light beam from the outside scenery 8. As a result, thelight beam of the display image 56 reflected by the front windshield 21and the light beam from the outside scenery 8 transmitted through theshield 21 are perceived by the occupant on the driver's seat 20 in thevehicle compartment 2 a.

As described above, the display image 56 is superimposed on the outsidescenery 8 as the virtual image imaged ahead of the front windshield 21so that the display image 56 can be viewed by the occupant in a visualrecognition region 7 within the vehicle compartment 2 a. Therefore, asshown in FIG. 5, the display region Ad in which the virtual image of thedisplay image 56 is displayed is set to a range in which the occupantcan visually recognize the image through the front windshield 21, and isalso included in the imaging region Ac of the outside camera 30 a andthe detection region Al of the brightness sensor 40 a.

As shown in FIG. 2, the HCU 54 mainly includes a microcomputer having aprocessor 54 a and a memory 54 b, and is connected to the HUD 50 and thein-vehicle network 6. The HCU 54 controls the virtual image display ofthe display image 56 by the HUD 50. At that time, the HCU 54 executes adisplay control based on, for example, information acquired or detectedby the ECUs 31 and 42 and the sensors 40 and 41, and information storedin the memory 54 b. The memory 54 b of the HCU 54 and the memories ofthe other various ECUs are configured with the use of one or multiplestorage media such as, for example, a semiconductor memory, a magneticmedium, an optical medium, or the like.

In this example, the HCU 54 reads out the display image 56 stored inadvance in the memory 54 b, and controls the virtual image display stateof the display image 56 by the HUD 50. For that purpose, the HCU 54executes the display control programs stored in advance in the memory 54b by the processor 54 a, thereby functionally realizing the steps of adisplay control flow shown in FIG. 7. The display control flow isstarted in response to an on-operation of the power switch 41 a, andcompleted in response to an off-operation of the switch 41 a. S in thedisplay control flow means each step.

As shown in FIG. 7, in S101 of the display control flow, the outsidecamera 30 a captures an image of the imaging region Ac of the outsidescenery 8, As a result, in S101, as shown in FIG. 6, the camera image 33configured by the imaging pixel values Tc for the respective colors ineach pixel is acquired.

In S102, the outside brightness Lo of the outside scenery 8 is detectedby the brightness sensor 40 a. As a result, in S102, the illuminance orluminance in the detection region Al superimposed on the imaging regionAc in the outside scenery 8 is acquired as the present outsidebrightness Lo shown in FIG. 5.

In S103, the imaging pixel value Tc as a correction conversion source isdetermined for a specific color from the imaging pixel value Tc of eachpixel in the camera image 33 acquired in S101. In the presentembodiment, this specific color is set in advance to be color G, but maybe alternatively set in advance as other colors such as R or B.

More specifically, in S103, first, a multiple pixel portion obtained byimaging a portion superimposed on a display region Ad is selected asspecific pixel portion Pc in the camera image 33 in S103 a, limited tothe outside scenery 8 on a near side (that is, on the vehicle 2 side) ofat least one of a vanishing point Hp and a horizon line Hl shown inFIGS. 3 and 5. At this time, in the present embodiment, a pixel areawhich is a fixed pixel area set in advance in the multiple pixel portioncontinuous in the vertical and horizontal directions as shown in FIG. 3and which is included in the detection region Al of the brightnesssensor 40 a in the outside scenery 8 and which captures an image of arange including the display region Ad is selected as the specific pixelportion Pc. Next, in S103, in S103 b of FIG. 7, the imaging pixel valuesTc for the specific color of the multiple pixel portion forming thespecific pixel portion Pc selected in S103 are averaged, so that anaverage pixel value Tcave as the imaging pixel value Tc, which is thecorrection conversion source, is calculated. At least one of thevanishing point Hp and the horizon line Hl serving as a reference of aselected position of the specific pixel portion Pc for averaging theimaging pixel values Tc in S103 is extracted by image processing of thecamera image 33 or at a fixed position corresponding to the mountingposition of the outside camera 30 a.

In S104, the average pixel value Tcave calculated in S103 as the imagingpixel value Tc for the specific color is converted into a correctionpixel value Tr as shown in FIG. 8 in accordance with the outsidebrightness Lo detected in S102. Specifically, the correction pixel valueTr represents a gradation value converted from the imaging pixel valueTc by a correction according to the outside brightness La in 256gradations of 0 to 255 so that an actual outside brightness Lo can bereflected regardless of a filtering process by the outside cameras 30 aor the ECU 31. Therefore, in the correction pixel value Tr according tothe present embodiment, a correlation with the imaging pixel value Tcfor the specific color is defined and stored in advance in the memory 54b as correction data Dr.

The correction data Dr defining the correlation of the correction pixelvalue Tr with respect to the imaging pixel value Tc in this manner isprepared in the form of a table for each predetermined outsidebrightness Lo (in an example of FIG. 8, a predetermined illuminance).However, in order to reduce a storage capacity of the memory 54 b, thecorrection data Dr between the prepared outside brightness Lo isinterpolated or extrapolated from the prepared correction data Dr of theoutside brightness Lo. In order to facilitate understanding of thedescription, FIG. 8 shows the correction data Dr indicating thecorrelation for each of the three outside brightness Lo and aninterpolation between those outside brightness, but actually, thecorrection data Dr indicating the correlation for each of the outsidebrightness Lo and the interpolation between the outside brightness Lo,which are more finely divided, are realized. The correction data Dr maybe prepared in the form of an arithmetic expression in whichinterpolation is unnecessary.

As described above, in S104, the correction pixel value Tr correspondingto the average pixel value Tcave for the specific color calculated inS103 is determined based on the correction data Dr corresponding to theoutside brightness Lo detected in S102.

Further, as shown in FIG. 7, in S105 subsequent to S104, the lightsource luminance value Sd of the light source unit 51 b that emits thelight of the display image 56 is controlled in association with thecorrection pixel value Tr converted in S104. Specifically, the lightsource luminance value Sd is expressed by the following Expression 1with the use of an initial setting value Sd0 of the light sourceluminance value Sd set in advance in the light source unit 51 b, and thecorrection pixel value Tr and a maximum value Tr max of the correctionpixel value (in this example, 255). FIG. 9 is a solid line graphillustrating the correlation between the initial setting value Sd0 andthe light source luminance value Sd according to Expression 1, where aratio Tr/Tr max between the correction pixel value Tr and the maximumvalue Tr max is 0.4. Therefore, in order to determine the light sourceluminance value Sd based on such a correlation, in the presentembodiment, a luminance value control data Dcs according to Expression 1is prepared in the form of a table as shown in FIG. 10, and is stored inadvance in the memory 54 b. The luminance value control data Dcs may beprepared in the form of an arithmetic expression representing Expression1.Sd=Sd0×Tr/Tr max  (Expression 1)

The light source luminance value Sd corresponding to the correctionpixel value Tr converted in S104 is determined in S105 based on theluminance value control data Dcs stored in the memory 54 b as describedabove. As a result, the light source unit 51 b is energized inaccordance with the determined light source luminance value Sd, therebyadjusting the virtual image display luminance Ld of the display image56. At that time, in the present embodiment, the display pixel value Tdaccording to the display unit 51 a is maintained at a fixed value.Therefore, the virtual image display luminance Ld of the display image56 shown in FIG. 5 is changed following the determined light sourceluminance value Sd, S105 described above is continued for a valid timeof the correction, and when the valid time has elapsed, the processreturns to S101.

From the viewpoint of the description above, in the first embodiment,the functional parts for executing the S103 b of the HCU 54 correspondto an averaging block. In addition, in the first embodiment, thefunctional part for executing S104 of the HCU 54 corresponds to aconversion block, and the functional part for executing S105 of the HCU54 corresponds to a display control block.

The operation and effects of the first embodiment described above willbe described below.

In the first embodiment, the correction pixel value Tr converted fromthe imaging pixel value Tc of the camera image 33 acquired by theoutside camera 30 a is a value corrected based on the correction data Drstored in the memory 54 b as a correlation with the imaging pixel valueTc. At that time, since the correction pixel value Tr is converted fromthe imaging pixel value Tc in accordance with the outside brightness Loof the outside scenery 8 detected by the brightness sensor 40 a, it iseasy to accurately reflect the actual outside brightness La. As aresult, in the display image 56 in which the light source luminancevalue Sd that determines the virtual image display luminance Ld iscontrolled corresponding to the correction pixel value Tr, a contrastdefect relative to the outside scenery 8 is less likely to occur, sothat the visibility can be ensured.

Further, as in the first embodiment, in the imaging region Ac of theoutside camera 30 a including the display region Ad, the actualbackground of the display image 56 displayed as a virtual image in thedisplay region Ad by the HUD 50 is imaged as the outside scenery 8.Thus, the correction pixel value Tr and the correspondingly controlledlight source luminance value Sd can reflect such actual backgroundimaging pixel value Tc. At the same time, as in the first embodiment, inthe detection region Al of the brightness sensor 40 a including thedisplay region Ad, the outside brightness Lo is detected in the actualbackground of the display image 56 displayed as a virtual image in thedisplay region Ad by the HUD 50. Thus, the correction pixel value Tr andthe correspondingly controlled light source luminance value Sd canreflect the outside brightness Lo of such an actual background.Therefore, according to the reflection action as described above, thereliability of the visibility securing effect can be enhanced by makingit difficult to surely cause the contrast defect.

In the first embodiment, the correction pixel value Tr is converted fromthe average pixel value Tcave calculated by averaging the imaging pixelvalues Tc of the specific pixel portion Pc which is the multiple pixelportion in the camera image 33. According to the average pixel valueTcave of the multiple pixel portion, an error caused by a local andaccidental variation of the imaging pixel value Tc can be reduced. As aresult, since the light source luminance value Sd controlledcorresponding to the correction pixel value Tr is less likely to cause acontrast defect caused by such a variation error of the imaging pixelvalue Tc, the reliability of the visibility securing effect can beenhanced.

Second Embodiment

A second embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 11, in S103 of a display control flowaccording to the second embodiment, imaging pixel values Tc ofrespective pixels of the multiple pixel portion forming a specific pixelportion Pc are compared with each other fora specific color (in thisembodiment, the color G) in S2103 b subsequent to S103 a. As a result,in S2103 b, as shown in FIG. 12, an imaging pixel value Tc of the samevalue or the same range is extracted from a most-pixel portion Pcm inwhich the number of pixels providing the imaging pixel value Tc of thesame value or the same range for the specific color is largest. In thisexample, FIG. 12 shows the most-pixel portion Pcm in which the number ofpixels providing the imaging pixel value Tc of the same value islargest. On the other hand, although not illustrated, the imaging pixelvalue Tc within the same range means the same range corresponding toeach imaging pixel value Tc of the specific pixel portion Pc in multipleranges that are separated from each other in advance every time theimaging pixel value Tc increases by a set amount.

As shown in FIG. 11, in the second embodiment, S103 shifts to S2104. InS2104, the imaging pixel value Tc of the most-pixel portion extracted inS2103 b for the specific color is converted into a correction pixelvalue Tr in accordance with an outside brightness La detected in S102.The conversion at that time is executed according to the firstembodiment. In other words, the correction pixel value Tr correspondingto the imaging pixel value Tc of the most-pixel portion Pcm extracted inS2103 b is determined based on the correction data Dr corresponding tothe outside brightness Lo detected in S102.

According to the second embodiment described above, the functional partfor executing S2103 b of the HCU 54 corresponds to an extraction block.In addition, in the second embodiment, the functional part for executingS2104 of the HCU 54 corresponds to a conversion block.

As described above, in the second embodiment, the imaging pixel valuesTc of the specific pixel portion Pc which is the multiple pixel portionin the camera image 33 are compared with each other, so that thecorrection pixel value Tr is converted from this imaging pixel value Tcof the most-pixel portion Pcm in which the number of pixels providingthe imaging pixel value Tc having the same value or within the samerange is the largest. According to the imaging pixel value Tc of themost-pixel portion Pcm, an error due to local and accidental fluctuationof the imaging pixel value Tc can be reduced. As a result, since thelight source luminance value Sd controlled corresponding to thecorrection pixel value Tr is less likely to cause a contrast defectcaused by such a variation error of the imaging pixel value Tc, thereliability of the visibility securing effect can be enhanced.

Third Embodiment

A third embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 13, in S103 of a display control flowaccording to the third embodiment, S3103 a and S3103 b are executed.

First, in S3103 a, a single-pixel portion obtained by capturing an imageof a portion overlapping with a display region Ad is selected as aspecific pixel portion Pc in a camera image 33 shown in FIG. 14, limitedto an outside scenery 8 on a near side of at least one of a vanishingpoint Hp and a horizon line Hl. At that time, in the third embodiment, afixed single-pixel portion set in advance as shown in FIG. 14 isselected as the specific pixel portion Pc. At that time, in the thirdembodiment, the imaging pixel value Tc for a specific color (in thethird embodiment, the color G) of the single-pixel portion forming theselected specific pixel portion Pc is extracted and stored in a memory54 b. The single-pixel portion as the specific pixel portion Pc is fixedto, for example, a pixel corresponding to the center of the displayregion Ad in the camera image 33.

Next, as shown in FIG. 13, in S3103 b, the imaging pixel values Tc forthe specific color are extracted in S3103 a multiple times and stored inthe memory 54 b, the average pixel value Tcave to be a correctionconversion source is calculated. At that time, the number of times ofuse of the imaging pixel value Tc in the calculation of the averagepixel value Tcave is set to a value capable of reducing an error due toa local and accidental variation of the imaging pixel value Tc. For thatreason, while the number of times of extracting the imaging pixel valueTc in S3103 a becomes smaller than the number of times of using theimaging pixel value Tc in S3103 b from a start of the display controlflow in response to on-operation of a power switch 41 a, the displaycontrol flow returns to S101 without executing S3103 b and subsequentsteps, although illustration is omitted.

In the third embodiment, the process shifts from S103 described above toS3104. In S3104, the average pixel value Tcave for the specific colorcalculated in S3103 b is converted into the correction pixel value Tr inaccordance with the outside brightness Lo detected in S102. Theconversion at that time is executed according to the first embodiment.In other words, the correction pixel value Tr corresponding to theaverage pixel value Tcave calculated in S3103 b is determined based onthe correction data Dr corresponding to the outside brightness Lodetected in S102.

In the third embodiment described above, the functional part forexecuting S3103 a of the HCU 54 corresponds to an extraction block, andthe functional part for executing the S3103 b of the HCU 54 correspondsto an averaging block. In addition, in the third embodiment, thefunctional part for executing S3104 of the HCU 54 corresponds to aconversion block.

As described above, in the third embodiment, the correction pixel valueTr is converted from the average pixel value Tcave calculated byextracting the imaging pixel values Tc of the specific pixel portion Pcwhich is a single-pixel portion of the camera image 33 a multiple timesand averaging the imaging pixel values Tc. According to the averagepixel value Tcave extracted multiple times, an error caused by the localand accidental variation in the imaging pixel value Tc can be reduced.As a result, since the light source luminance value Sd controlledcorresponding to the correction pixel value Tr is less likely to cause acontrast defect caused by such a variation error of the imaging pixelvalue Tc, the reliability of the visibility securing effect can beenhanced.

Fourth Embodiment

A fourth embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 15, in S103 of a display control flowaccording to the fourth embodiment, imaging pixel values Tc of therespective pixels of the multiple pixel portion forming a specific pixelportion Pc are compared with each other for a specific color (in thefourth embodiment, the color G) in S4103 b subsequent to S103 a, As aresult, in S4103 b, as shown in FIG. 16, the maximum imaging pixel valueTc of a maximum-value pixel portion Pcl which gives the maximum imagingpixel value Tc is extracted for the specific color. At that time, in thefourth embodiment, the extracted imaging pixel value Tc is stored in amemory 54 b.

In S103 of the display control flow according to the fourth embodiment,the display control flow shifts from S4103 b to S4103 c as shown in FIG.15. In S4103 c, the imaging pixel values Tc of the maximum-value pixelportions Pcl extracted in S4103 b multiple times and stored in thememory 54 b are averaged for the specific color, so that the averagepixel value Tcave to be a correction conversion source is calculated. Atthat time, the number of times of use of the imaging pixel value Tc inthe calculation of the average pixel value Tcave is set to a valuecapable of reducing an error due to a local and accidental variation ofthe imaging pixel value Tc. For that reason, while the number of timesof extracting the imaging pixel value Tc in S4103 b becomes smaller thanthe number of times of using the imaging pixel value Tc in S4103 c froma start of the display control flow in response to on-operation of apower switch 41 a, the display control flow returns to S101 withoutexecuting S4103 c and subsequent steps, although illustration isomitted.

In the fourth embodiment, the process shifts from S103 to S4104. InS4104, the average pixel value Tcave for the specific color calculatedin S4103 c is converted into the correction pixel value Tr in accordancewith the outside brightness Lo detected in S102. The conversion at thattime is executed according to the first embodiment. In other words, thecorrection pixel value Tr corresponding to the average pixel value Tcavecalculated in S4103 c is determined based on the correction data Drcorresponding to the outside brightness Lo detected in S102.

In the fourth embodiment described above, the functional part forexecuting S4103 b of the HCU 54 corresponds to an extraction block, andthe functional part for executing the S4103 c of the HCU 54 correspondsto an averaging block. In addition, in the fourth embodiment, thefunctional part for executing the S4104 of the HCU 54 corresponds to aconversion block.

As described above, in the fourth embodiment, the imaging pixel value Tcof the specific pixel portion Pc which is the multiple pixel portion inthe camera image 33 is compared with each other to extract the imagingpixel value Tc of the maximum-value pixel portion Pcl which gives themaximum imaging pixel value Tc, Therefore, the correction pixel value Tris converted from the average pixel value Tcave calculated by extractingthe imaging pixel values Tc of the maximum-value pixel portion Pclmultiple times and averaging the imaging pixel values Tc. According tothe average pixel value Tcave extracted multiple times, an error causedby the local and accidental variation in the imaging pixel value Tc canbe reduced. As a result, since the light source luminance value Sdcontrolled corresponding to the correction pixel value Tr is less likelyto cause a contrast defect caused by such a variation error of theimaging pixel value Tc, the reliability of the visibility securingeffect can be enhanced.

Fifth Embodiment

A fifth embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 17, in S5105 of a display controlflow according to the fifth embodiment, the light source luminance valueSd of the light source unit 51 b for a specific color is controlled soas to correspond to the correction pixel value Tr converted in S104, andalso so as to correspond to target weighting data Dwo. At the same time,in S5105, the display pixel value Td of each pixel in the display image56 is controlled so as to correspond to the correction pixel value Tr ofeach of the colors, including the specific color, converted in S104 andalso so as to correspond to the target weighting data Dwo. Further, inthe fifth embodiment, the average pixel values Tcave calculated in S103as the imaging pixel values for each color in S103 are converted in S104into respective ones of the correction pixel value Tr corresponding tothe average pixel values Tcave of each color. Here, the target weightingdata Dwo is a numerical value for weighting the correction on the lightsource luminance value Sd more than that of the display pixel value Td.Therefore, the target weighting data Dwo is set and stored in advance inthe memory 54 b such that the value for weighting the light sourceluminance value Sd is larger than the value for weighting the displaypixel value Td and a sum of those values is set to 1. For example, thetarget weighting data Dwo is set to 0.25 or the like smaller than 0.5 inthe case of the display pixel value Td, and to 0.75 or the like largerthan 0.5 in the case of the light source luminance value Sd.

The light source luminance value Sd is represented by Expression 2 belowwith the use of the target weighting data Dwo, the initial setting valueSd0 of the light source luminance value Sd set in advance in the lightsource unit 51 b, and the correction pixel value Tr and the maximumvalue Tr max of the correction pixel value Tr. FIG. 18A is a solid linegraph illustrating the correlation between the initial setting value Sd0and the light source luminance value Sd according to Expression 2, wherea ratio Tr/Tr max between the correction pixel value Tr and the maximumvalue Tr max is 0.4. Therefore, in order to determine the light sourceluminance value Sd based on such a correlation, in the fifth embodiment,a luminance value control data Dcs according to Expression 2 is preparedin the form of a table as shown in FIG. 19A, and is stored in advance inthe memory 54 b. The luminance value control data Dcs may be prepared inthe form of an arithmetic expression representing Expression 2.Sd=Dwo×Sd0×Tr/Tr max  (Expression 2)

On the other hand, the display pixel value Td is expressed for eachcolor by Expression 3 below with the use of the target weighting dataDwo, an initial setting value Td0 of the display pixel value Td set inadvance for each pixel of the display image 56 in the display unit 51 a,and the correction pixel value Tr of a specific color and the maximumvalue Tr max of the correction pixel value Tr. FIG. 18B is a solid-linegraph illustrating for each color a correlation between the initialsetting value Td0 and the display pixel value Td according to Expression3, where a ratio Tr/Tr max between the correction pixel value Tr and themaximum value Tr max is 0.4. Therefore, in order to determine thedisplay pixel value Td based on such a correlation, in the fifthembodiment, pixel value control data Dct according to Expression 3 isprepared in the form of a table as shown in FIG. 19B, and is stored inadvance in a memory 54 b. The pixel value control data Dct may beprepared in the form of an arithmetic expression expressing Expression3.Td=Dwo×Td0×Tr/Tr max  (Expression 3)

In the fifth embodiment, in S5105, the light source luminance value Sdcorresponding to not only the correction pixel value Tr for the specificcolor converted in S104 but also the target weighting data Dwo in theluminance value control data Dcs is determined based on the luminancevalue control data Dcs stored in the memory 54 b. At the same time, inS5105, the display pixel value Td for each color corresponding to notonly the correction pixel value Tr of each color converted in S104 butalso the target weighting data Dwo in the pixel value control data Dctis determined based on the pixel value control data Dct stored in thememory 54 b. As a result, the virtual image display luminance Ld of thedisplay image 56 changes by following the determined light sourceluminance value Sd and the determined display pixel value Td for each ofthe colors. It should be noted that S5105 is continued for a valid timeof the correction, and when the valid time has elapsed, the processreturns to S101.

In the fifth embodiment, the functional part for executing S5105 of theHCU 54 corresponds to a display control block.

As described above, in the fifth embodiment, not only the light sourceluminance value Sd but also the display pixel value Td are controlled inaccordance with the correction pixel value Tr which accurately reflectsthe actual outside brightness Lo. At that time, according to the targetweighting data Dwo to which those control targets are made tocorrespond, the light source luminance value Sd is given a correctionweight more than that of the display pixel value Td. Due to this, withthe combination the light source luminance value Sd of as the prioritycontrol target and the display pixel value Td as the auxiliaryadjustment target, the resolution of the virtual image display luminanceLd can be finely set to reduce the contrast defect, so that thereliability of the visibility securing effect can be enhanced.

Other Embodiments

Although a plurality of embodiments of the present disclosure have beendescribed above, the present disclosure is not construed as beinglimited to these embodiments, and can be applied to various embodimentsand combinations within a scope without departing from the spirit of thepresent disclosure.

In Modification 1 relating to the first to fifth embodiments, inaddition to or instead of the HCU 54, at least a part of the displaycontrol flows may be realized functionally (that is, in a software-likemanner) by the cooperation of one or more types of an ECU forcontrolling other display elements of the vehicle 2 and the ECUs 31, 42.In Modification 2 relating to the first to fifth embodiments, at least apart of the display control flow may be realized by hardware using oneor multiple ICs or the like, instead of the display control flow beingrealized functionally by using the HCU 54 or the like.

In Modification 3 relating to the first to fifth embodiments, thestorage of the display image 56 may be realized by a memory built in theHUD 50 or another display element of the vehicle 2, or by a cooperationof the built-in memory and the memory 54 b. In Modification 4 relatingto the first to fifth embodiments, at least one type of data among thedata Dr, Dcs, Dwo, and Dct may be realized by a memory built in the HUD50 or another display element of the vehicle 2, or by a cooperation ofthe built-in memory and the memory 54 b.

In Modification 5 relating to the first to fifth embodiments, forexample, a pixel portion that changes in accordance with a time, avehicle speed, or the like may be selected as the specific pixel portionPc. In Modifications 6 relating to the first, second, fourth, and fifthembodiments, a predetermined number of discontinuous pixel portions inthe pixel portion continuous in the vertical and horizontal directionsmay be selected as the specific pixel portion Pc.

In Modification 7 related to the first to fifth embodiments, a pixelportion of the camera image 33, which includes at least one of thevanishing point Hp or the horizon line Hl in the outside scenery 8 (thatis, extending vertically), may be selected as the specific pixel portionPc. In Modification 8 relating to the first to fifth embodiments, apixel portion of the camera image 33 captured at a location higher thanat least one of the vanishing point Hp or the horizon line Hl in theoutside scenery 8 may be selected as the specific pixel portion Pc.

In Modification 9 relating to the first to fifth embodiments, a part orthe whole of the display region Ad may be deviated from the imagingregion Ac of the outside camera 30 a, In Modification 9, the imagingregion Ac may be set in addition to the front of the vehicle compartment2 a. In Modification 10 relating to the first to fifth embodiments, apart or the whole of the display region Ad may be out of the detectionregion Al of the brightness sensor 40 a, In Modification 10, thedetection region Al may be set at a position other than the front of thevehicle compartment 2 a.

In Modification 11 relating to the first to fifth embodiments, as shownin FIG. 20, at least one of the outside cameras 30 a and the brightnesssensor 40 a may be provided exclusively for the HUD 50. FIG. 19 showsModification 11 in which both the outside camera 30 a and the brightnesssensor 40 a are provided exclusively for the HUD 50.

In Modification 12 relating to the first to fifth embodiments, as shownin FIG. 21, the imaging pixel value Tc may represent gradation valuesfor the luminance (Y), the color difference (U) between Y and B, and thecolor difference (V) between Y and R. In other words, in Modification12, the imaging pixel value Tc of each pixel is generated by the outsidecamera 30 a in a YUV data format, and the correction data Dr is preparedfor each of Y, U, and V as shown in FIG. 22. Therefore, in the case ofModification 12, the first to fifth embodiments can be realized byreplacing the specific color and each of the colors with a specific oneof Y, U, and V (Y in an example of FIG. 22) and each of Y, U, and V,respectively.

In Modification 13 relating to the third embodiment, a value obtained byaveraging the imaging pixel values Tc of the multiple pixel portion maybe extracted multiple times in accordance with the first embodiment, andthe correction pixel value Tr may be converted from the average pixelvalue Tcave obtained by further averaging the extracted values multipletimes. In Modification 14 relating to the third embodiment, the imagingpixel value Tc of the most-pixel portion Pcm may be extracted multipletimes in accordance with the second embodiment, and the correction pixelvalue Tr may be converted from the average pixel value Tcave obtained byaveraging the extracted values multiple times.

In Modification 15 relating to the fifth embodiment, the conversion ofthe correction pixel value Tr may be performed from the imaging pixelvalue Tc of the most-pixel portion Pcm in the specific pixel portion Pcin accordance with the second embodiment. In Modification 16 relating tothe fifth embodiment, the average pixel value Tcave obtained byaveraging the imaging pixel values Tc of the single-pixel portionsextracted multiple times in each of the specific pixel portions Pc maybe converted into the correction pixel value Tr in accordance with thethird embodiment. In Modification 17 relating to the fifth embodiment,the average pixel value Tcave obtained by averaging the imaging pixelvalues Tc of the maximum-value pixel portions Pcl extracted multipletimes in each of the specific pixel portions Pc may be converted intothe correction pixel value Tr in accordance with the fourth embodiment.

In Modification 18 relating to the fifth embodiment, the targetweighting data Dwo may be reflected in the correction pixel value Tr inthe correction data Dr, instead of being reflected in Expressions 2 and3 in which the luminance value control data Dcs and the pixel valuecontrol data Dct respectively follow. In the case of Modification 18, avalue obtained by multiplying the correction pixel value Tr described inthe first embodiment by the target weighting data Dwo as the correctionpixel value Tr corresponding to the light source luminance value Sd isintroduced into Expression 2 in which Dwo=1 (in other words, same asExpression 1). In the case of Modification 18, a value obtained bymultiplying the correction pixel value Tr described in the fifthembodiment by the target weighting data Dwo as the correction pixelvalue Tr corresponding to the display pixel value Td is introduced intoExpression 3 in which Dwo=1.

In Modification 19 relating to the fifth embodiment, the targetweighting data Dwo for weighting the correction on the display pixelvalue Td rather than the light source luminance value Sd may be adopted.In this Modification 19, by including the case where the weighting ofthe light source luminance value Sd is 0, it is possible to control onlythe display pixel value Td in accordance with the correction pixel valueTr.

The invention claimed is:
 1. A vehicle display device provided in avehicle mounted with an outside camera that acquires a camera image byimaging outside scenery and a brightness sensor that detects an outsidebrightness of the outside scenery, the vehicle display device configuredto project a display image onto a projection member, which transmits theoutside scenery, to display the display image as a visible virtual imagein a visual recognition region in a vehicle compartment, the vehicledisplay device comprising: a head-up display that emits light to formthe display image; a memory that stores, as correction data, acorrelation of a correction pixel value with respect to an imaging pixelvalue, the correction pixel value being converted from the imaging pixelvalue forming the camera image according to the outside brightnessdetected by the brightness sensor; a conversion block that converts,based on the correction data stored in the memory, the imaging pixelvalue the camera image acquired by the outside camera into thecorrection pixel value in accordance with the outside brightnessdetected by the brightness sensor; and a display control block thatcontrols a light source luminance value of the head-up display incorrespondence with the correction pixel value converted from theimaging pixel value by the conversion block.
 2. The vehicle displaydevice according to claim 1, wherein the head-up display displays thedisplay image as the virtual image in a display region, and the displayregion is included in an imaging region of the outside camera and adetection region of the brightness sensor.
 3. The vehicle display deviceaccording to claim 1, further comprising an average block thatcalculates an average pixel value by averaging imaging pixel values of amultiple pixel portion of the camera image acquired by the outsidecamera, wherein the conversion block converts the average pixel valuecalculated by the averaging block into the correction pixel value. 4.The vehicle display device according to claim 1, further comprising anextraction block that extracts the imaging pixel value of a most-pixelportion, in which the number of pixels is greatest given a same imagingpixel value or within a same range, by comparing imaging pixel values ofa multiple pixel portion in the camera image acquired by the outsidecamera, wherein the conversion block converts the imaging pixel value ofthe most-pixel portion extracted by the extraction block into thecorrection pixel value.
 5. The vehicle display device according to claim1, further comprising: an extraction block that extracts the imagingpixel value of a single-pixel portion from the camera image acquired bythe outside camera; and an averaging block that calculates an averagepixel value by averaging imaging pixel values of multiple single pixelportions extracted over a plurality of times by the extraction block,wherein the conversion block converts the average pixel value calculatedby the average block into the correction pixel value.
 6. The vehicledisplay device according to claim 1, further comprising: an extractionblock that extracts the imaging pixel value of a maximum-value pixelportion having a largest imaging pixel value by comparing imaging pixelvalues of a multiple pixel portion in the camera image acquired by theoutside camera; and an averaging block that calculates an average pixelvalue by averaging imaging pixel values of multiple largest-value pixelportions extracted over a plurality of times by the extraction block,wherein the conversion block converts the average pixel value calculatedby the average block into the correction pixel value.
 7. The vehicledisplay device according to claim 1, wherein the memory stores targetweighting data for weighting correction of the light source luminancevalue more than correction of a display pixel value of the display imageformed by the head-up display, and the display control block controlsthe light source luminance value and the display pixel value incorrespondence with the correction pixel value converted from theimaging pixel value by the conversion block and in correspondence withthe target weighting data stored in the memory.
 8. A vehicle displaysystem for a vehicle, comprising: an outside camera configured toacquire a camera image by imaging outside scenery; a brightness sensorthat detects an outside brightness of the outside scenery; a head-updisplay configured to emit light to project a display image onto alight-transmissive projection member of the vehicle, the projecteddisplay image being displayed as a visible virtual image; a memory thatstores, as correction data, a correlation of a correction pixel valuewith respect to an imaging pixel value forming the camera image, thecorrection pixel value being converted from the imaging pixel valueaccording to the outside brightness detected by the brightness sensor;and one or more processors collectively programmed to: convert, based onthe correction data stored in the memory, the imaging pixel value in thecamera image acquired by the outside camera into the correction pixelvalue in accordance with the outside brightness detected by thebrightness sensor, and control a light source luminance value of thehead-up display in correspondence with the correction pixel valueconverted from the imaging pixel value.